This invention pertains to magnetic pick up tools.
U.S. Pat. No. 2,517,325 to Lamb, in disclosing a magnetic probe which is intended to provide different amounts of magnetic force for an instrumentation purpose, discloses a probe in which a bar magnet can be extended outside of a magnetic shielding material so as to provide for concentration of the magnetic lines of force at the exposed pole. (See FIG. 2.)
U.S. Pat. No. 4,813,729 to Speckhart discloses a magnetic retrieval tool in which the magnet is contained within a removable shielding so as to reduce its magnetic attraction along the side of the magnet. The device is claimed to have the capability of attracting off its front face but having limited attraction from its side faces to other magnetic materials.
U.S. Pat. No. 2,993,723 to Twachtman and others discloses a flexible magnetic retrieving device.
U.S. Pat. No. 3,169,791 to Twachtman shows a pick up in which the magnet is press fit within the end of the housing and is exposed rather than working through a magnetic pole.
U.S. Pat. No. 2,285,440 to Kaiser shows a magnet, slidably mounted within a non-magnetic rod, which is connected to a pull cable so that the magnet can be allowed to be extended out to pick up objects or, alternatively, retracted into a sleeve so as to weaken the magnetic force and release the object being attracted.
U.S. Pat. No. 5,265,887 to Stelmach shows a magnetic pick-up tool encased within an outer sleeve so that the entire tool can be positioned next to an object to be picked up and then the magnet extended to attract the object. Alternatively, the magnet can be retracted within the sleeve so as to prevent the magnet from being attracted to objects while the tool is being positioned to a place of pick up.
U.S. Pat. No. 512,381 to Keyers discloses an early form of magnetic pick up tool where the tip of the magnet is within a sleeve and is extended so as to provide for a pick up effect.
U.S. Pat. No. 3,789,336 to Gordin discloses a retractable holder for a magnet which provides for two positions for the magnetic device: exposed to provide for magnetic attraction and retracted within a shielding sleeve so as to reduce the magnetic attraction of the device.
A device in which an elongate bar magnet is provided with one pole embedded in a non-magnetic handle and the other pole extending distance away so as to provide for nearly parallel magnetic lines of force along the side of the device and concentration of the lines of force at the end of the device is not shown in this art